Next possible upgrade. Need some advice!

Hello! I’ve been using a Nikon D3000 for years. I’m looking to upgrade this year to a full-frame mirrorless. I’ve got a NIKKOR18-140mm, NIKKOR 35mm, and Sigma 10-20mm on hand. I’m looking at the Nikon Z6 or Sony a7 III. I like to do a lot of travel photos, low-light, or long-exposure shots.

I’m leaning more towards the Sony. Are these good choices for an upgrade? My budget is at $2000. Also, if I opt for a camera that’s not Nikon, how hard will it be to utilize the lenses I currently own? I’m open to any and all recommendations or advice! I’ve been researching for the past few hours, but I’m still stuck. Thank you!